The present invention relates to a chromatic confocal sensor and a measurement method that uses it.
From the past, the chromatic confocal technique has been used for measuring a height of an object to be measured and the like. For example, Japanese Patent Application Laid-open No. 2011-39026 (hereinafter, referred to as Patent Document 1) discloses a chromatic confocal displacement meter (hereinafter, referred to as chromatic sensor) as shown in FIG. 1. In the chromatic sensor, a color to be focused on a work changes on a one-on-one basis according to a height (displacement) of the work. By extracting light of a color to be focused on the work and specifying the color (optical wavelength), the height of the work that is in a one-on-one relationship with the color is measured (paragraphs [0002], [0003], etc. in specification of Patent Document 1).
In the chromatic sensor disclosed in Patent Document 1, specification of an optical wavelength is performed using the fact that a phase difference (optical channel difference) corresponding to an optical wavelength is caused between mutually-perpendicular polarization components that pass through a wave plate constituted of a birefringent crystal and the like. Accordingly, it becomes possible to realize a measurement that satisfies a long operating distance, a fine measurement spot, a small error due to a tilt, high resolution, and high-speed responsiveness at the same time (paragraphs [0030], [0035], etc. in specification of Patent Document 1).